day 4

Author: sachuverma

Leetcode Daily Challenge/March-2021/04. Intersection of Two Linked Lists.cpp

@@ -0,0 +1,81 @@
+/*
+Intersection of Two Linked Lists
+================================
+
+Write a program to find the node at which the intersection of two singly linked lists begins.
+
+Example 1:
+Input: intersectVal = 8, listA = [4,1,8,4,5], listB = [5,6,1,8,4,5], skipA = 2, skipB = 3
+Output: Reference of the node with value = 8
+Input Explanation: The intersected node's value is 8 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [4,1,8,4,5]. From the head of B, it reads as [5,6,1,8,4,5]. There are 2 nodes before the intersected node in A; There are 3 nodes before the intersected node in B.
+
+Example 2:
+Input: intersectVal = 2, listA = [1,9,1,2,4], listB = [3,2,4], skipA = 3, skipB = 1
+Output: Reference of the node with value = 2
+Input Explanation: The intersected node's value is 2 (note that this must not be 0 if the two lists intersect). From the head of A, it reads as [1,9,1,2,4]. From the head of B, it reads as [3,2,4]. There are 3 nodes before the intersected node in A; There are 1 node before the intersected node in B.
+
+Example 3:
+Input: intersectVal = 0, listA = [2,6,4], listB = [1,5], skipA = 3, skipB = 2
+Output: null
+Input Explanation: From the head of A, it reads as [2,6,4]. From the head of B, it reads as [1,5]. Since the two lists do not intersect, intersectVal must be 0, while skipA and skipB can be arbitrary values.
+Explanation: The two lists do not intersect, so return null.
+
+Notes:
+If the two linked lists have no intersection at all, return null.
+The linked lists must retain their original structure after the function returns.
+You may assume there are no cycles anywhere in the entire linked structure.
+Each value on each linked list is in the range [1, 10^9].
+Your code should preferably run in O(n) time and use only O(1) memory.
+*/
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode(int x) : val(x), next(NULL) {}
+ * };
+ */
+
+class Solution
+{
+public:
+  ListNode *getIntersectionNode(ListNode *headA, ListNode *headB)
+  {
+    int sizeA = 0, sizeB = 0;
+    auto tempA = headA, tempB = headB;
+
+    while (tempA)
+    {
+      sizeA++;
+      tempA = tempA->next;
+    }
+    while (tempB)
+    {
+      sizeB++;
+      tempB = tempB->next;
+    }
+
+    tempA = headA;
+    tempB = headB;
+
+    while (sizeA > sizeB)
+    {
+      tempA = tempA->next;
+      sizeA--;
+    }
+    while (sizeB > sizeA)
+    {
+      tempB = tempB->next;
+      sizeB--;
+    }
+
+    while (tempA != tempB)
+    {
+      tempA = tempA->next;
+      tempB = tempB->next;
+    }
+
+    return tempA;
+  }
+};

Leetcode Daily Challenge/March-2021/README.md

@@ -5,3 +5,4 @@
 | 1.  | [Distribute Candies](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/588/week-1-march-1st-march-7th/3657/) | [cpp](./01.%20Distribute%20Candies.cpp) |
 | 2.  | [Set Mismatch](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/588/week-1-march-1st-march-7th/3658/)       |    [cpp](./02.%20Set%20Mismatch.cpp)    |
 | 3.  | [Missing Number](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/588/week-1-march-1st-march-7th/3659/)       |    [cpp](./03.%20Missing%20Number.cpp)    |
+| 4.  | [Intersection of Two Linked Lists](https://leetcode.com/explore/challenge/card/march-leetcoding-challenge-2021/588/week-1-march-1st-march-7th/3660/)       |    [cpp](./04.%20Intersection%20of%20Two%20Linked%20Lists.cpp)    |